Medical Compass: Reducing kidney stone risk

Lowering your sodium intake can help

By David Dunaief, M.D.

Although it’s possible to have a kidney stone without symptoms, more often they present with the classic symptoms of blood in the urine and colicky pain. The pain can be intermittent or constant, and it can range from dull to extremely painful, described by some as being worse than giving birth, being shot or being burned. The pain can radiate from the kidneys to the bladder and even to the groin in males, depending on the obstruction (1).

Stones are usually diagnosed through the symptoms and either abdominal x-rays or non-contrast CT scans.

Unfortunately, the first line treatment for passing kidney stones — at least small ones — involves supportive care. This means that patients are given pain medications and plenty of fluids until the stone(s) pass. Usually stones that are smaller than four millimeters pass spontaneously. Stones closest to the opening of the urethra are more likely to pass through on their own (2).

Generally, if you’ve passed a kidney stone, you know it.

In the case of a stone too large to pass naturally, a urologist may use surgery, ultrasound, or a combination of methods to break it into smaller pieces, so you can pass it. Unfortunately, once a patient forms one stone, the possibility of having others increases significantly over time. The good news is that there are several lifestyle changes you can make to reduce your risk.

How much water do you need to drink?

First, it is very important to stay hydrated and drink plenty of fluids, especially if you have a history of stone formation (3). You don’t have to rely on drinking lots of water to accomplish this, though. Increasing your consumption of fruits and vegetables that are moisture-filled can help, as well.

Do supplements play a role in stone formation?

One of the simplest methods is to reduce your intake of calcium supplements, including foods fortified with calcium. There are two types of stones. Calcium oxalate is the dominant one, occurring approximately 80 percent of the time (4). Calcium supplements, therefore, increase the risk of kidney stones.

When physicians started treating women for osteoporosis with calcium supplements, the rate of kidney stones increased by 37 percent (5). According to findings from the Nurses’ Health Study, those who consumed highest amount of supplemental calcium were 20 percent more likely to have kidney stones than those who consumed the lowest amount (6). It did not matter whether study participants were taking calcium citrate or calcium carbonate supplements.

Interestingly, calcium from dietary sources actually has the opposite effect, decreasing risk. In the same study, those participants who consumed the highest amount of dietary calcium had a 35 percent reduction in risk, compared to those who were in the lowest group. Paradoxically, calcium intake shouldn’t be too low, either, since that also increases kidney stone risk. Changing your source of calcium is an important key to preventing kidney stones.

What role does sodium play in stone formation?

Again, in the Nurses’ Health Study, participants who consumed 4.5 grams of sodium per day had a 30 percent higher risk of kidney stones than those who consumed 1.5 grams per day (6). The reason is that increased sodium causes increased urinary excretion of calcium. When there is more calcium going through the kidneys, there is a higher chance of stones.

Does protein play a role in stone formation?

Animal protein may play a role. In a five-year, randomized clinical trial, men who reduced their consumption of animal protein to approximately two ounces per day, as well as lowering their sodium, were 51 percent less likely to experience a kidney stone than those who consumed a low-calcium diet (7). These were men who had histories of stone formation.

The reason animal protein may increase the risk of calcium oxalate stones more than vegetable protein is that animal protein’s higher sulfur content produces more acid. This acid is neutralized by release of calcium from the bone (8). That calcium can then promote kidney stones.

Does blood pressure impact kidney stones?

Some medical conditions may increase the likelihood of stone formation. For example, in a cross-sectional study with Italian men, those with high blood pressure had a two times greater risk of kidney stones than those who had a normal blood pressure (9). Amazingly, it did not matter whether or not the patients were treated for high blood pressure with medications; the risk remained. This is just one more reason to treat the underlying cause of blood pressure, not just the symptoms. The most productive way to avoid the potentially excruciating experience of kidney stones is to make these relatively simple lifestyle changes. The more that you implement, the lower your likelihood of stones.

References:

(1) emedicine January 1, 2008. (2) J Urol. 2006;175(2):575. (3) J Urol. 1996;155(3):839. (4) N Engl J Med. 2004;350(7):684. (5) Kidney Int 2003;63:1817–23. (6) Ann Intern Med. 1997;126(7):497-504. (7) N Engl J Med. 2002 Jan 10;346(2):77-84. (8) J Clin Endocrinol Metab. 1988;66(1):140. (9) BMJ. 1990;300(6734):1234.

Dr. David Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com or consult your personal physician.